The present invention generally relates to wireless communication systems. In particular, the present invention relates to a method for conserving battery life in a subscriber unit.
Wireless communications have long been used to enable communication between a subscriber unit and a base station without the need for restrictive hardwire connections. The cordless phone, for example, allows communication between a handset and a base. As another example, cellular systems allow a subscriber unit (earth stations, mobile terminals, cellular phones, and the like) to communicate with a radio tower or satellite.
The marriage of cellular transceiver technology with additional interface hardware at the subscriber end allows the cable that runs between a building (such as a home) and a central switching office of a telephone system to be eliminated. That cable is replaced by a radio communications link. A subscriber unit at a particular location may then use a cellular transceiver and associated hardware to interface that transceiver into the telephone cabling of the subscriber""s building. This technology is known as a wireless local loop. The combination of cellular transceiver and interface hardware is commonly known as a fixed access unit.
A significant problem that arises when wireless local loops are used in place of traditional subscriber-to-system cable links is that power for the subscriber unit circuitry can no longer be easily provided by the communications service provider, because a physical link over a cable to the subscriber unit is no longer maintained. Thus, the subscriber must supply power to operate the subscriber unit, including the cellular transceiver and interface hardware, as well as the subscriber""s communications equipment that is connected to the subscriber unit via the interface hardware.
It is inevitable that there will on occasion be losses of power at locations where a subscriber unit, such as a fixed access unit, is being used. This is particularly true in areas where wireless local loop technology is most frequently used today (e.g., developing countries and rural areas where it is difficult to run landlines), as electric power is frequently intermittent in those locales. In order for communications to remain possible during such power outages, many fixed access units are equipped with a battery back up system.
In the past, however, a fixed access unit could not use battery power for an extended period of time. This caused communications links during line power failures to be short lived and unreliable. Therefore, a need exists for a method that conserves battery life of a subscriber unit as long as possible, allowing for communications service to continue for the maximum possible time.
It is an object of the present invention to provide a method to greatly increase the battery life of a subscriber unit.
Another object of the present invention is to provide such a method that is compatible with existing cellular standards.
One or more of the foregoing objects are met in whole or in part by a preferred embodiment of the present invention, which provides a method for extending battery life in a subscriber unit in contact with a system node of a wireless communication network. The method establishes a current inactivity level. The method then periodically checks the state of a power failure flag (which is set when line power is not available and clear otherwise).
When the power failure flag is clear and there is no line power present, the method sets the power failure flag and sets a timer to expire after a period of time based on the current inactivity level. When the power-failure flag is set and line power is present, the method clears the power failure flag and performs a default inactivity level registration with the system node requesting to use the system default inactivity level. When the power failure flag is set, no line power is present and the timer has expired, the method performs an incremental inactivity level registration with the system node requesting to use the next highest inactivity level. The method may, however, perform the incremental registration only when the current inactivity level is not at the system maximum inactivity level. A second preferred embodiment of the method of the invention uses a smart battery in lieu of the timer mechanism for determining when to adjust the inactivity level.